Technical Field
Embodiments of the invention relate generally to superconducting magnets and, more specifically, to a system and method for magnetic resonance imaging one or more subjects.
Discussion of Art
Magnetic resonance imaging (“MRI”) is a widely accepted and commercially available technique for obtaining digitized visual images representing the internal structure of objects having substantial populations of atomic nuclei that are susceptible to nuclear magnetic resonance (“NMR”). Many MRI systems use superconductive magnets to scan a subject/patient via imposing a strong main magnetic field on the nuclei in the subject to be imaged. The nuclei are excited by a radio frequency (“RF”) signal/pulse transmitted by a RF coil at characteristics NMR (Larmor) frequencies. By spatially disturbing localized magnetic fields surrounding the subject and analyzing the resulting RF responses from the nuclei as the excited protons relax back to their lower energy normal state, a map or image of these nuclei responses as a function of their spatial location is generated and displayed. An image of the nuclei responses provides a non-invasive view of a subject's internal structure.
Many MRI systems utilize gradient coils to spatially encode the RF responses so that the locations of the nuclei corresponding to the RF response can be determined. Many gradient coils are driven by electrical wires wrapped into coils. As used herein with respect to gradient coils, the terms “driven” and “drive” refer to the generation of a magnetic field resulting from the flow of electrical current through the electrical wires of the gradient coil. Generation of a magnetic field by a gradient coil, however, results in electrical resistance within the electrical wires of the gradient coil. The generation of a magnetic field by a gradient coil may also produce eddy currents within other components of an MRI system, e.g., other gradient coils, RF shields, shim coils, etc., which also contribute to the electrical resistance in the electrical wires of the gradient coil. The amount of electrical resistance within the electrical wires of a gradient coil partially determines the amount of electrical power required to drive the gradient coil, and the amount of power required to drive the gradient coil is usually directly proportional to the cost of operating the encompassing MRI system.
As a result, some MRI systems seek to reduce the amount of resistance within the electrical wires of a gradient coil by mitigating/reducing the amount/magnitude of eddy currents generated in the various components of an MRI by the gradient coil. For example, some MRI systems utilize hollow copper conductors. Hollow copper conductors, however, are typically very expensive to manufacture.
What is needed, therefore, is an improved MRI system and method for imaging one or more subjects.